Fix missing "All" filter translation key on shop discover page

t("common.all") didn't resolve to anything on web (unlike the RN app,
which does have that key) — verified in the browser, where the chip
rendered as the literal string "common.all". Added a proper
shops.allFilter key instead of guessing at an existing one.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/shops/discover/page.tsx

@@ -44,7 +44,7 @@ export default function ShopDiscoverPage() {
                   : "border-neutral-200 text-neutral-700 dark:border-neutral-700 dark:text-neutral-300"
               )}
             >
-              {t("common.all")}
+              {t("shops.allFilter")}
             </button>
             <button
               type="button"

src/locales/en/common.json

@@ -3000,6 +3000,7 @@
     "comparisonTitle": "Compare shop prices",
     "noListingsForProduct": "No shops found for this product",
     "discoverTitle": "Shops",
+    "allFilter": "All",
     "pinterestFilter": "Pinterest",
     "pinterestProductLabel": "Pinterest product",
     "pinterestProductHint": "This product will show up under the shop's Pinterest filter",

src/locales/fa/common.json

@@ -2999,6 +2999,7 @@
     "comparisonTitle": "مقایسه قیمت فروشگاه‌ها",
     "noListingsForProduct": "فروشگاهی برای این کالا یافت نشد",
     "discoverTitle": "فروشگاه‌ها",
+    "allFilter": "همه",
     "pinterestFilter": "پینترستی",
     "pinterestProductLabel": "محصول پینترستی",
     "pinterestProductHint": "این کالا در فیلتر پینترستی فروشگاه نمایش داده می‌شود",